Parallel ruler



FIG. 1 is a top perspective view of a parallel ruler showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a side elevational view thereof;

FIG. 4 is an elevational view thereof; and,

FIG. 5 is a bottom plan view thereof. 

The ornamental design for a parallel ruler, as shown and described. 